A high performance sintered NdFeB magnet and its preparation method

Abstract

The present invention discloses a high-performance sintered NdFeB magnet and a preparation method thereof. The high-performance sintered NdFeB magnet comprises raw materials for preparing the NdFeB magnet, including a main alloy and an auxiliary alloy, wherein the auxiliary alloy does not contain Fe and Co elements; the microstructure of the NdFeB magnet comprises a matrix phase and a rare earth-rich grain boundary phase, wherein the matrix phase is (RE / RE')2(F) 14 B, where F is Fe and Co, the Co content is 0-3, the mass ratio of Fe and RE / RE' in the rare earth-rich grain boundary phase is 1:(1.4-7), RE is Nd or PrNd, and RE' is one or more of Pr, Ho, Dy, and Tb. This NdFeB magnet has high magnetic properties.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a high-performance sintered NdFeB magnet and a preparation method thereof. Background Art

[0002] Sintered NdFeB magnets, with their superior magnetic properties and cost-effectiveness, are widely used in industries such as new energy vehicles, wind power generation, white goods, consumer electronics, and industrial motors. With the growing demand for high-performance magnets, rare earth prices have also been rising. In particular, the prices of heavy rare earth elements, Tb and Dy, which are used extensively in sintered NdFeB, have seen a significant increase. Therefore, the key focus of recent technological developments in the industry has been on reducing or eliminating the use of heavy rare earth elements in the production of high-performance magnets.

[0003] Currently, the main technology for reducing heavy rare earth content is grain boundary diffusion (GBD). This involves preparing heavy rare earth metals or alloys into powders of a specific size. This powder is then deposited onto the magnet surface through printing, sputtering, coating, or vapor deposition. Through appropriate heat treatment, the heavy rare earth elements diffuse along the grain boundaries into the magnet interior. The heavy rare earth elements are primarily distributed in the outermost epitaxial regions of the main phase grains, optimizing the demagnetizing exchange coupling of the main phase grains and significantly increasing the coercivity of the magnet. While maintaining the same performance, this significantly reduces the amount of heavy rare earth elements used compared to conventional processes.

[0004] Grain boundary diffusion technology is very effective in utilizing heavy rare earths, but is limited by product specifications. Currently, it is less effective for large-sized products (oriented thickness greater than 1 cm), and has disadvantages such as poor consistency and poor diffusion operability for ultra-small-sized products.

[0005] The dual alloy process is also one of the current process routes for reducing heavy rare earth. Its principle is to design two different alloys, with the main phase being close to Nd2Fe without heavy rare earth. 14 The mass ratio of the volume fraction of the B phase is that the auxiliary phase is mainly composed of a high anisotropy field rare earth rich phase (HR2Fe14B), and the high anisotropy field phase is coated around the main phase to achieve the purpose of improving the coercive force of the magnet.

[0006] Patent application CN 106601407 A discloses a method for increasing the coercivity of NdFeB magnets. The method comprises mixing R1-Fe-B-M1 powder as the primary alloy powder and R1-R2-Fe-B-M1 powder as the secondary alloy powder, so that the secondary alloy powder is evenly distributed on the surface of the primary alloy powder. R1 comprises Nd and Pr; M1 is selected from one or more of Co, Cu, Zr, Al, Ga, Si, Mn, Ni, Zn, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb, and Bi; and R2 is selected from one or more of Gd, Dy, Tb, Ho, Er, Tm, Yb, Lu, and Y. This patent application utilizes highly compatible primary and secondary alloy powders to significantly increase the coercivity of NdFeB magnets while reducing the amount of heavy rare earth elements used. However, the above invention patent application has a relatively high content of Fe and Co elements in the grain boundary phase, which has a certain influence on the coercive force of the NdFeB magnet.

[0007] The dual alloy process is simple and convenient, not limited by product specifications, and the elements in the magnet are evenly distributed, with good performance consistency. However, the conventional dual alloy design mainly forms REFe(Co)B phase, which not only reduces the Nd2Fe 14 B phase ratio, and H cj The improvement effect of (intrinsic coercivity) is far smaller than that of the grain boundary diffusion process, which has a certain limiting effect on the preparation of high-performance magnets.

[0008] Therefore, it is of great significance to develop a new dual alloy process to reduce the amount of heavy rare earth while improving the performance of the magnet. Summary of the Invention

[0009] The invention provides a high-performance sintered NdFeB magnet having high magnetic properties.

[0010] The present invention provides a high-performance sintered NdFeB magnet. The raw materials for preparing the NdFeB magnet include a main alloy and an auxiliary alloy, and the auxiliary alloy does not contain Fe and Co elements.

[0011] The main alloy comprises the following chemical components in terms of mass percentage: RE x B y M z T w F 1-x-y-z-w , RE is rare earth Nd or PrNd, B is boron, M is at least one of Nb, Zr, and Ti, T is Cu and Ga, and F includes Fe and Co, wherein the Co content is 0-3 wt.%, and the Fe content is not 0;

[0012] Among them, the content of each element is x: 27~30wt.%, y: 0.9~1.1wt.%, z: 0.05~0.25wt.%, and w: 0.1~0.5wt.%.

[0013] The microstructure of the NdFeB magnet includes a matrix phase and a rare earth-rich grain boundary phase, wherein the matrix phase is (RE / RE')2(F) 14 B, wherein F is Fe and Co, the content of Co is 0-3, the mass percentage of Fe and RE / RE' in the rare earth-rich grain boundary phase is 1: (1.4~8), wherein RE is Nd or PrNd, and RE' is one or more of Pr, Ho, Dy, and Tb.

[0014] Compared with the conventional dual alloy technology, the dual alloy process of the present invention does not add Fe and Co elements to the auxiliary alloy. During the phase transformation process of mixed sintering with the main alloy, there is very little or no new (RE / RE')2Fe(Co) in the matrix phase. The matrix phase of the obtained NdFeB magnet contains (RE / RE')2Fe 14 The volume fraction of B is extremely high, and the magnet has a high remanence.

[0015] On the other hand, because the auxiliary alloy is a rare earth B alloy without Fe and Co elements, an auxiliary phase structure dominated by antiferromagnetism is obtained, that is, a rare earth-rich grain boundary phase. The rare earth-rich grain boundary phase is wrapped around the main phase. The uniform distribution of the antiferromagnetic auxiliary phase around the main phase effectively isolates the exchange coupling between the main phases, thereby improving the anti-demagnetization ability of the magnet. While maintaining a high remanence, the coercive force can also be greatly improved.

[0016] Preferably, the NdFeB magnet is prepared by a dual alloy process.

[0017] Preferably, the grain boundary rare earth-rich phase is one or more of Pr3Fe, Nd3Fe, and (PrNd)3Fe.

[0018] Preferably, in the microstructure of the NdFeB magnet, the mass ratio of the main alloy to the auxiliary alloy is (94-98): (2-6).

[0019] The present invention improves the coercive force of the magnet while achieving excellent magnetic properties of the magnet by controlling the content of the rare earth-rich grain boundary phase.

[0020] Preferably, the D50 particle size of the main alloy is 3.5-4.5 μm, and the D50 particle size of the auxiliary alloy is 2.5-3.5 μm.

[0021] The present invention controls the particle size of the main alloy and the auxiliary alloy to make the magnet have better magnetic properties, while avoiding the reduction of oxidation resistance due to excessive surface area. By further refining the auxiliary alloy particles, they are effectively dispersed to the grain boundaries between the main phase grains, thereby enhancing the demagnetizing coupling effect between the main phases and significantly improving the coercive force of the magnet. Therefore, high-performance permanent magnets with high remanence and high coercive force can be prepared.

[0022] Preferably, in the element T, the mass percentage of Cu and Ga is 1:(1.2~1.5).

[0023] The present invention improves the stability of the magnet by controlling the content of the T element, promotes the distribution of the RE / RE' phase, and cooperates with the RE / RE' phase to enhance the coercive force of the magnet. Since the price of Ga is 30-40 times that of Cu, the present invention provides an appropriate amount of Cu to replace Ga, achieving similar effects at a more appropriate cost.

[0024] The appropriate amount of Co provided by the present invention can increase the Curie temperature of the magnet and improve the thermal properties of the magnet. The addition of Co is related to the practical application of the magnet and avoids a sharp deterioration of the magnet performance. At the same time, Co is a strategic material and some terminal applications will limit the Co content.

[0025] Since the auxiliary alloy of the present invention does not contain Co and Fe, and the Co content in the main alloy is low, the proportion of the matrix phase in the magnet provided by the present invention is very high, while the proportion of the soft magnetic Fe-Co phase is extremely low, which is beneficial to improving the magnetic properties.

[0026] Preferably, the auxiliary alloy comprises the following chemical components in terms of mass percentage: RE' 1-a-b-c B a M b c , RE' is one or more of Pr, Ho, Dy, Tb, B is boron, M is at least one of Nb, Zr, Ti, Cu and Ga, where the mass percentage of Cu and Ga is 1: (1.2~1.5);

[0027] Among them, the content of each element is a: 0.5~5wt.%; b: 0~2wt.%, and c: 4~10wt.%.

[0028] The auxiliary alloy provided by the present invention does not contain Fe and Co elements. The surplus Fe element in the main element is used to form a rare earth-rich grain boundary phase with the rare earth elements, M and T elements in the auxiliary alloy, which is beneficial to improving the coercive force, thereby avoiding or reducing the formation of Fe-Co soft magnetic phase and destroying the coercive force.

[0029] Preferably, the mass percentage of the main alloy in the raw material is 94%-98%, and the mass percentage of the auxiliary alloy in the raw material is 2%-6%.

[0030] The present invention avoids affecting the residual magnetic strength (Br) by controlling the proportion of the auxiliary alloy, and can also form sufficient rare earth-rich grain boundary phase to improve the coercive force of the magnet.

[0031] Preferably, the NdFeB magnet has a coercive force of 17-19 kOe, a remanence of 14.25-14.5 kGs, and a squareness of more than 98%.

[0032] On the other hand, the present invention also provides a method for preparing the high-performance sintered NdFeB magnet, comprising:

[0033] Preparation of master alloy RE x B y M z T w F 1-x-y-z-w Powder and auxiliary alloy RE' 1-a-b-c B a M b T c Powder, wherein RE is rare earth Nd or PrNd, B is boron, M is at least one of Nb, Zr, and Ti, T is Cu and Ga, F contains Fe and Co, Co content is 0-3wt.%, Fe content is not 0, RE' is one or more of Pr, Ho, Dy, and Tb, and the content of each element is x: 27-30wt.%, y: 0.9-1.1wt.%, z: 0.05-0.25wt.%, w: 0.1-0.5wt.%, a: 0.5-5wt.%, b: 0-2wt.%, and c: 4-10wt.%.

[0034] The main alloy RE x B y M z T w F 1-x-y-z-w Powder and auxiliary alloy RE' 1-a-b-c B a M b T c The powders are mixed uniformly to obtain a mixed powder, and the mixed powder is pressed into a compact by a magnetic field forming method or a hot pressing and hot deformation method;

[0035] sintering the compact into a blank in vacuum or inert gas;

[0036] The blank is subjected to multi-stage aging treatment to obtain a high-performance sintered NdFeB magnet.

[0037] Preferably, the multi-stage aging treatment includes three-stage aging treatment;

[0038] Among them, the temperature of the first stage of aging treatment is 890~930℃;

[0039] The temperature of the second aging treatment is 580~680℃;

[0040] The temperature of the third aging treatment is 420~520℃.

[0041] The present invention controls the temperature of the first and second aging treatments to allow rare earth elements in the magnet to diffuse to the grain boundaries and eliminate stress. The present invention controls the temperature of the third aging treatment to make the rare earth elements more evenly distributed.

[0042] Preferably, the master alloy RE x B y M z T w F 1-x-y-z-w A method for preparing a powder, comprising:

[0043] S11, by chemical formula RE x B y M z T w F 1-x-y-z-w The elemental raw materials are weighed and vacuum-melted, and then cast at a temperature of 1350-1450°C to obtain a main phase cast sheet with a thickness of 0.2-0.35 mm, a grain spacing of 3.5-4.5 μm, and oxygen and nitrogen contents passing therethrough are less than 120 ppm and less than 30 ppm, respectively.

[0044] S12. The main phase casting is processed by conventional hydrogen crushing process to obtain main phase hydrogen crushed powder: the hydrogen absorption pressure of hydrogen crushing is 1.5~2kg / cm 2 , the dehydrogenation temperature is 500℃~600℃, the oxygen content of the hydrogen powder is <1000ppm, and the hydrogen content is <1000ppm;

[0045] S13. Jet-mill the main phase hydrogen powder to obtain a main alloy with a D50 particle size of 3.5-4.5 μm.

[0046] Preferably, the auxiliary alloy RE' 1-a-b-c B a M b T c A method for preparing a powder, comprising:

[0047] S21, according to the chemical formula RE' 1-a-b-c B a M b T cThe elemental raw materials are weighed and vacuum-melted, and then cast at a temperature of 1480-1520°C to obtain auxiliary phase casting sheets with a thickness of 0.05-0.25 mm, a grain spacing of 0.5-2 μm, an oxygen content of less than 120 ppm, and a nitrogen content of less than 30 ppm;

[0048] S22, hydrogen crushing of the auxiliary phase casting: first, heat the auxiliary phase casting to 300-350℃ and introduce hydrogen to absorb hydrogen once, with the hydrogen absorption pressure of 3-4kg / cm 2 Then vacuum heat to 800~900℃ for secondary heat preservation and hydrogen absorption, the hydrogen absorption pressure is 3~4kg / cm 2 Finally, dehydrogenation is carried out at 400-500°C to obtain auxiliary hydrogen powder with an oxygen content of <1000ppm and a hydrogen content of 3000-5000ppm;

[0049] S23. The auxiliary phase hydrogen powder is subjected to air flow milling, and the oxygen content of the air flow milling system is controlled to be less than 10 ppm to obtain an auxiliary alloy with a D50 particle size of 2.5-3.5 μm.

[0050] More preferably, the carbon content of rare earth elements in the elemental raw materials is less than 200ppm, the carbon content of pure iron is less than 30ppm, and the carbon content of other elements is less than 500ppm. The present invention avoids the influence of the carbon content in the elemental raw materials on the performance of the magnet by controlling the carbon content.

[0051] Preferably, the master alloy RE x B y M z T w F 1-x-y-z-w Powder and auxiliary alloy RE' 1-a-b-c B a M b T c Before the powders are evenly mixed to obtain the mixed powder, 0.05-0.2 wt.% of the total weight of the main alloy and the auxiliary alloy is added as a lubricant, and the oxygen content during the powder mixing process is less than 100 ppm.

[0052] Preferably, the green compact is prepared by a magnetic field forming method, wherein the magnetic field strength is not less than 1.5 T, the forming pressure is greater than 160 MPa, the atmosphere is controlled to have an oxygen content of less than 100 ppm, and the green compact density is not less than 4.4 g / cm 3 .

[0053] Preferably, in step S4, the sintering temperature is 1050-1075° C., the sintering vacuum is better than 0.1 Pa, and the sintering time is greater than 6 hours.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The present invention uses an auxiliary alloy that does not contain Fe and Co elements as a raw material, minimizes the content of Co in the rare earth-rich grain boundary phase, and minimizes the formation of the Fe-Co soft magnetic phase that can significantly reduce the coercive force of the magnet, while increasing the proportion of the matrix phase. At the same time, the surplus Fe and RE / RE' are utilized to form a rare earth-rich grain boundary phase at the grain boundary without reducing the proportion of the matrix phase, thereby increasing the coercive force and improving the magnetic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0057] Figure 1 1 is the metallographic structure diagram of the main alloy rapid solidification casting sheet obtained in Example 1;

[0058] Figure 2 This is a scanning electron microscope image of the magnet obtained in Example 1;

[0059] Figure 3 This is the metallographic structure diagram of the magnet produced by the existing dual alloy process technology. DETAILED DESCRIPTION

[0060] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. Unless the context clearly indicates otherwise, as used herein, the singular is intended to include the plural. It should also be understood that the term "comprising" does not specifically refer to a particular feature, field, integer, step, action, element, and / or component, but excludes the presence or addition of other features, fields, integers, steps, actions, elements, components, and / or groups.

[0061] If a part is described as being on top of another part, then other parts can be directly on top of the other part or there can be other parts in between. When a part is described as being directly on top of another part, there can be no other parts in between. Although not otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art. For terms that have definitions in dictionaries, they should be interpreted as having the same meaning as that in the relevant technical literature and the content disclosed in this article, and their meaning should not be interpreted in an idealized or overly formal sense.

[0062] The concept of the present invention is further elaborated below.

[0063] According to a preferred embodiment of the present invention, a high-performance sintered NdFeB magnet is made of a main alloy and an auxiliary alloy, and the mass ratio of the main alloy to the auxiliary alloy is (94~98):(2~6).

[0064] The main alloy element ratio is: RE x B y M z T w F 1-x-y-z-w , wherein RE is rare earth Nd or PrNd, B is boron; M is at least one of Nb, Zr, and Ti; T is a combination of Cu and Ga, wherein the Cu:Ga ratio is 1:(1.2~1.5); F contains Fe and Co, the Co content is 0~3wt.%, and the Fe content is not 0; the components are matched according to the following mass percentages: x: 27~30wt.%; y: 0.9~1.1wt.%, z: 0.05~0.25wt.%, and w: 0.1~0.5wt.%.

[0065] The auxiliary alloy element ratio is: RE' 1-a-b-c B a M b T c , wherein RE' is one or more of Pr, Ho, Dy, and Tb; B is boron; M is at least one of Nb, Zr, and Ti; T is a combination of Cu and Ga, with a Cu:Ga ratio of 1:(1.2-1.5); and the auxiliary alloys are combined in the following weight percentages: a: 0.5-5wt.%; b: 0-2wt.%; and c: 4-10wt.%. The high-performance sintered NdFeB magnet has a coercivity exceeding 17kOe, a remanence above 14.25kGs, and a squareness exceeding 98%.

[0066] Furthermore, the D50 particle size of the main alloy is 3.5-4.5 μm, and / or the D50 particle size of the auxiliary alloy is 2.5-3.5 μm.

[0067] The auxiliary alloy is pulverized by HDDR+ air flow grinding and then coated around the main phase. The uniform distribution of the antiferromagnetic auxiliary phase around the main phase effectively isolates the exchange coupling between the main phases, thereby improving the anti-demagnetization ability of the magnet. While maintaining a high remanence, the coercive force can also be greatly improved, and the final squareness of the magnet is excellent.

[0068] According to a preferred embodiment of the present invention, a method for preparing a low (no) heavy rare earth high performance sintered NdFeB magnet comprises the following steps:

[0069] A. The main phase alloy and the auxiliary phase alloy are prepared according to the above rules.

[0070] B. The configured main phase alloy and auxiliary phase alloy are vacuum melted separately to prepare rapid solidification casting sheets.

[0071] C. The main phase and auxiliary phase rapid solidification casting sheets are subjected to hydrogen crushing and air flow grinding respectively to produce micron-sized fine powder.

[0072] D. Prepare the main phase and auxiliary phase fine powders in a certain proportion, add lubricant and antioxidant and mix.

[0073] E. In a low oxygen and nitrogen atmosphere, the mixed powder is oriented and pressed into shape under a high magnetic field, and then isostatically pressed under ultra-high pressure to obtain a compact.

[0074] F. The compact is vacuum sintered under vacuum, and then subjected to multi-stage aging treatment to obtain a high-performance NdFeB magnet.

[0075] In step A, raw materials with low carbon content are preferred, with the carbon content of rare earth elements controlled at <200 ppm, the carbon content of pure iron at <30 ppm, and the carbon content of other components at <500 ppm.

[0076] In step B, the main phase alloy is preferably cast at a temperature of 1350°C to 1450°C, the thickness of the casting is 0.2mm to 0.35mm, and the grain spacing is controlled to be 3.5 to 4.5μm; the auxiliary phase alloy is preferably cast at a temperature of 1480°C to 1520°C, the thickness of the casting is 0.05mm to 0.25mm, and the grain spacing is controlled to be 0.5 to 2μm. The oxygen content in each casting is <120ppm, and the nitrogen content is <30ppm.

[0077] In step C, the main phase casting adopts conventional hydrogen crushing process, and the hydrogen absorption pressure of hydrogen crushing is 1.5~2kg / cm 2 The dehydrogenation temperature is 500℃~600℃, and the hydrogen powder obtained has O<1000ppm and H<1000ppm. The hydrogen absorption pressure of the auxiliary phase casting is 3~4kg / cm 2 During hydrogen absorption, the alloy is first heated to 300-350°C and hydrogen is introduced. The alloy is then vacuum-heated to 800-900°C for a second heat-insulation process. Finally, the alloy is dehydrogenated at 400-500°C. The resulting auxiliary hydrogen powder retains a high hydrogen content to prevent oxidation. The hydrogen content is preferably controlled between 3000ppm and 5000ppm, and the oxygen content is preferably <1000ppm. The main phase alloy particle size distribution (D50) is controlled within the range of 3.5-4.5μm, while the auxiliary phase alloy particle size distribution is 2.5-3.5μm. During grinding, the oxygen content in the jet mill system is controlled to be <10ppm.

[0078] In step D, the main and auxiliary phase alloy powders with particle sizes meeting the requirements are mixed in a certain proportion, wherein the auxiliary phase is added in a proportion of 2%-6%. In addition, 0.05%-0.2% of a lubricant (preferably zinc stearate or borate) based on the total weight of the two alloy powders is added and stirred in a mixer for about 2-5 hours. After mixing, the mixture is placed in a sealed steel bottle with an oxygen content of <100 ppm and allowed to stand for more than 12 hours.

[0079] In step E, the mixed powder is oriented in a magnetic field in an atmosphere with an oxygen content of less than 100 ppm and a magnetic field strength of not less than 1.5 T. After being pressed by a press, it is vacuum packaged and then further pressed by isostatic pressing at a pressure greater than 160 MPa to obtain a density of not less than 4.4 g / cm 3 of the compact.

[0080] In step F, the isostatically pressed green compact is placed in a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering temperature is 1050°C~1075°C, the sintering vacuum is better than 0.1Pa, and the sintering time is greater than 6 hours. The multi-stage aging process is a three-stage process, and the process temperatures of each stage are 890~930°C, 580~680°C, and 420~520°C, respectively. The aging time of each stage should be greater than 3 hours. The second and third stages of aging cooling adopt N2-filled air cooling, and the cooling rate should be greater than 10°C / min. Rapid cooling prevents the formation of impurities, which is beneficial to improving the H content of the product. cj and obtain higher demagnetization squareness.

[0081] The present invention is further described in detail below with reference to specific embodiments for better understanding and implementation.

[0082] Example 1: This example provides a method for preparing low-heavy rare earth high-performance sintered NdFeB, and the operating steps are as follows:

[0083] Step 1: Prepare low-heavy rare earth main alloy A and auxiliary alloy B, respectively melt the prepared main alloy A and auxiliary alloy B raw materials into alloys through vacuum melting, and then cast them at high temperature to form main alloy A casting sheet and auxiliary alloy B casting sheet.

[0084] In order to obtain excellent microstructure, the main alloy A and the auxiliary alloy B are prepared by selecting different process parameters. In this embodiment, the casting temperature of the main alloy A is 1420℃~1450℃, the linear speed of the casting copper roller is 0.9~1.5m / s, and the cooling water temperature is 10℃~30℃. The thickness of the main alloy rapid solidification casting sheet obtained is 0.2mm~0.4mm, the grain spacing is 3.5~4.5μm, and it has an excellent columnar microstructure. Figure 1 As shown, the gray is (RE / RE')2Fe 14 Phase B, white, is a rare earth-rich phase.

[0085] The casting temperature of auxiliary alloy B is 1500℃~1520℃, the linear speed of the casting copper roller is 5~10m / s, and the cooling water temperature is 2℃~8℃ to obtain a fine and uniform microstructure with a thickness of 0.05mm~0.15mm and a grain spacing of 0.5~2μm.

[0086] In this embodiment, the weight percentages of the main alloy A are: 29% PrNd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, and 68.42% Fe; the weight percentages of the auxiliary alloy B are: 40% Dy, 47.5% Pr, 1% B, 4% Zr, 3% Cu, and 4.5% Ga. The specific compositions are shown in Table 1.

[0087] Step 2: Prepare hydrogen crushed powder, hydrogen crush the main alloy A casting, and the hydrogen absorption pressure is 1.8kg / cm 2 Until saturation, then dehydrogenation, the dehydrogenation temperature is 550 ℃, the obtained hydrogen powder has an O content of 852ppm and a H content of 780ppm; the hydrogen absorption pressure of the auxiliary alloy B casting is 3.5kg / cm 2 When absorbing hydrogen, it is first heated to 300℃ and kept warm for 0.5 hours before hydrogen is introduced. Then it is vacuumed and heated to 880℃ for secondary hydrogen absorption until saturation. Finally, it is kept warm at 450℃ for dehydrogenation. The dehydrogenation time is controlled reasonably. The final H content of the auxiliary phase hydrogen powder is measured to be 4236ppm, and the O content is 912ppm.

[0088] Step 3: Jet-mill the main and auxiliary powders. Grind the main alloy A hydrogenated powder to a D50 particle size of 3.89 μm using a jet mill, and the auxiliary alloy B hydrogenated powder to a D50 particle size of 2.73 μm using a jet mill. Mix the main phase powder A and auxiliary phase powder B in a weight ratio of 98:2. Add 0.06% of a liquid lubricant to each and stir for 3 hours.

[0089] Step 4: The mixed powder is oriented in a magnetic field with an oxygen content of less than 100 ppm and a magnetic field strength of 1.8 T. After pressing, it is vacuum-sealed and then isostatically pressed at a pressure of 180 MPa to a density of 4.4 g / cm 3 of the compact.

[0090] Step 5: Place the isostatically pressed compact in a vacuum sintering furnace for vacuum sintering and aging. The sintering process is 1072°C for 8 hours, and the sintering vacuum is better than 0.1 Pa. The aging process is 900°C for 3 hours, 650°C for 3 hours, and 495°C for 5 hours. Cooling during the second and third aging stages is performed using nitrogen-filled air cooling at a cooling rate of 12°C / min.

[0091] Example 2: This example differs from Example 1 in that, in step 3, main alloy A and main alloy B are mixed in a weight ratio of 96:4. The process parameters of other steps are the same as those of Example 1.

[0092] Example 3: This example provides a method for preparing heavy rare earth-free high-performance sintered NdFeB, and the operating steps are as follows:

[0093] Step 1: Prepare heavy rare earth-free main alloy A and auxiliary alloy B, respectively, vacuum melt the prepared main alloy A and auxiliary alloy B raw materials into alloys, and then cast them at high temperature to form main alloy A castings and auxiliary alloy B castings.

[0094] To achieve a superior microstructure, different process parameters were selected for the main alloy A and the auxiliary alloy B. In this embodiment, the main alloy A was cast at a temperature of 1420°C to 1450°C, the copper roller linear speed was 0.9 to 1.5 m / s, and the cooling water temperature was 10°C to 30°C. This yielded a superior columnar microstructure with a thickness of 0.2 mm to 0.4 mm and a grain spacing of 3.5 to 4.5 μm.

[0095] The casting temperature of auxiliary alloy B is 1500℃~1520℃, the linear speed of the casting copper roller is 5~10m / s, and the cooling water temperature is 2℃~8℃, so as to obtain a fine and uniform microstructure with a thickness of 0.05mm~0.15mm and a grain spacing of 0.5~2μm.

[0096] In this embodiment, the main alloy A is composed of 29% PrNd, 0.91% B, 0.2% Zr, 0.2% Cu, 0.3% Ga, 0.8% Co, and 68.59% Fe in weight percentage, and the auxiliary phase alloy B is composed of 87.7% Pr, 0.8% B, 4% Zr, 3% Cu, and 4.5% Ga in weight percentage. The specific composition is shown in Table 1.

[0097] Step 2: Prepare hydrogen crushed powder, hydrogen crush the main alloy A casting, and the hydrogen absorption pressure is 1.8kg / cm 2 Until saturation, then dehydrogenation, the dehydrogenation temperature is 550 ℃, the obtained hydrogen powder has an O content of 780ppm and a H content of 769ppm; the hydrogen absorption pressure of the auxiliary alloy B casting is 3.5kg / cm 2 When absorbing hydrogen, it is first heated to 300℃ and kept warm for 0.5 hours before hydrogen is introduced. Then it is vacuumed and heated to 880℃ for secondary hydrogen absorption until saturation. Finally, it is kept warm at 450℃ for dehydrogenation. The dehydrogenation time is controlled reasonably. The final H content of the auxiliary phase hydrogen powder is measured to be 3800ppm, and the O content is 890ppm.

[0098] Step 3: Jet milling and mixing of main and auxiliary fine powders: Main Alloy A hydrogenated powder was jet milled to a particle size D50 of 3.92 μm, and auxiliary Alloy B was jet milled to a particle size D50 of 2.85 μm. Main Alloy A and auxiliary Alloy B were mixed in a weight ratio of 98:2, and 0.06% liquid lubricant was added to each and stirred for 3 hours.

[0099] Step 4: The mixed powder is oriented in a magnetic field with an oxygen content of less than 100 ppm and a magnetic field strength of 1.8 T. After pressing, it is vacuum-sealed and then isostatically pressed at a pressure of 180 MPa to a density of 4.4 g / cm 3 of the compact.

[0100] Step 5: Place the isostatically pressed compact in a vacuum sintering furnace for vacuum sintering and aging. The sintering process is 1072°C for 8 hours, with a vacuum level better than 0.1 Pa. The aging process is 900°C for 3 hours, 650°C for 3 hours, and 495°C for 5 hours. Cooling during the second and third aging stages is performed using nitrogen-filled air cooling at a rate of 12°C / min.

[0101] Example 4: This example differs from Example 3 in that, in step 3, main alloy A and main alloy B are mixed in a weight ratio of 96:4. The process parameters of other steps are the same as those of Example 1.

[0102] Example 5: Step 1: Prepare a low-heavy rare earth main alloy A and auxiliary alloy B, and respectively melt the prepared main alloy A and auxiliary alloy B raw materials into alloys by vacuum melting, and then cast them at high temperature to form main alloy A castings and auxiliary alloy B castings.

[0103] In order to obtain excellent microstructure, different process parameters are selected for the preparation of main alloy A and auxiliary alloy B. In this embodiment, the casting temperature of main alloy A is 1420℃~1450℃, the linear speed of the casting copper roller is 0.9~1.5m / s, and the cooling water temperature is 10℃~30℃. The thickness of the main alloy rapid solidification casting sheet obtained is 0.2mm~0.4mm, the grain spacing is 3.5~4.5μm, and it has an excellent columnar microstructure, as shown in the attached figure. Figure 1 As shown, the gray is (RE / RE')2Fe 14 Phase B, white, is a rare earth-rich phase.

[0104] The casting temperature of auxiliary alloy B is 1500℃~1520℃, the linear speed of the casting copper roller is 5~10m / s, and the cooling water temperature is 2℃~8℃ to obtain a fine and uniform microstructure with a thickness of 0.05mm~0.15mm and a grain spacing of 0.5~2μm.

[0105] In this embodiment, the weight percentages of the main alloy A are: 29% Nd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, 68.42% Fe, and the weight percentages of the auxiliary alloy B are: 40% Dy, 47.5% Pr, 1% B, 4% Zr, 3% Cu, 4.5% Ga. The specific compositions are shown in Table 1.

[0106] Step 2: Prepare hydrogen crushed powder, hydrogen crush the main alloy A casting, and the hydrogen absorption pressure is 1.8kg / cm 2 Until saturation, then dehydrogenation, the dehydrogenation temperature is 550 ℃, the obtained hydrogen powder has an O content of 852ppm and a H content of 780ppm; the hydrogen absorption pressure of the auxiliary alloy B casting is 3.5kg / cm 2 When absorbing hydrogen, it is first heated to 300℃ and kept warm for 0.5 hours before hydrogen is introduced. Then it is vacuumed and heated to 880℃ for secondary hydrogen absorption until saturation. Finally, it is kept warm at 450℃ for dehydrogenation. The dehydrogenation time is controlled reasonably. The final H content of the auxiliary phase hydrogen powder is measured to be 4236ppm, and the O content is 912ppm.

[0107] Step 3: Jet-mill the main and auxiliary powders. Grind the main alloy A hydrogenated powder to a D50 particle size of 3.89 μm using a jet mill, and the auxiliary alloy B hydrogenated powder to a D50 particle size of 2.73 μm using a jet mill. Mix the main phase powder A and auxiliary phase powder B in a weight ratio of 98:2. Add 0.06% of a liquid lubricant to each and stir for 3 hours.

[0108] Step 4: The mixed powder is oriented in a magnetic field with an oxygen content of less than 100 ppm and a magnetic field strength of 1.8 T. After pressing, it is vacuum-sealed and then isostatically pressed at a pressure of 180 MPa to a density of 4.4 g / cm 3 of the compact.

[0109] Step 5: Place the isostatically pressed compact in a vacuum sintering furnace for vacuum sintering and aging. The sintering process is 1072°C for 8 hours, and the sintering vacuum is better than 0.1 Pa. The aging process is 900°C for 3 hours, 650°C for 3 hours, and 495°C for 5 hours. Cooling during the second and third aging stages is performed using nitrogen-filled air cooling at a cooling rate of 12°C / min.

[0110] Example 6: Step 1: Prepare a low-heavy rare earth main alloy A and auxiliary alloy B, and respectively melt the prepared main alloy A and auxiliary alloy B raw materials into alloys by vacuum melting, and then cast them at high temperature to form main alloy A castings and auxiliary alloy B castings.

[0111] In order to obtain excellent microstructure, different process parameters are selected for the preparation of main alloy A and auxiliary alloy B. In this embodiment, the casting temperature of main alloy A is 1420℃~1450℃, the linear speed of the casting copper roller is 0.9~1.5m / s, and the cooling water temperature is 10℃~30℃. The thickness of the main alloy rapid solidification casting sheet obtained is 0.2mm~0.4mm, the grain spacing is 3.5~4.5μm, and it has an excellent columnar microstructure, as shown in the attached figure. Figure 1 As shown, the gray is (RE / RE')2Fe 14 Phase B, white, is a rare earth-rich phase.

[0112] The casting temperature of auxiliary alloy B is 1500℃~1520℃, the linear speed of the casting copper roller is 5~10m / s, and the cooling water temperature is 2℃~8℃ to obtain a fine and uniform microstructure with a thickness of 0.05mm~0.15mm and a grain spacing of 0.5~2μm.

[0113] In this embodiment, the weight percentages of the main alloy A are: 29% PrNd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, and 68.42% Fe. The weight percentages of the auxiliary alloy B are: 40% Tb, 47.5% Pr, 1% B, 4% Zr, 3% Cu, and 4.5% Ga. The specific compositions are shown in Table 1.

[0114] Step 2: Prepare hydrogen crushed powder, hydrogen crush the main alloy A casting, and the hydrogen absorption pressure is 1.8kg / cm 2 Until saturation, then dehydrogenation, the dehydrogenation temperature is 550 ℃, the obtained hydrogen powder has an O content of 852ppm and a H content of 780ppm; the hydrogen absorption pressure of the auxiliary alloy B casting is 3.5kg / cm 2 When absorbing hydrogen, it is first heated to 300℃ and kept warm for 0.5 hours before hydrogen is introduced. Then it is vacuumed and heated to 880℃ for secondary hydrogen absorption until saturation. Finally, it is kept warm at 450℃ for dehydrogenation. The dehydrogenation time is controlled reasonably. The final H content of the auxiliary phase hydrogen powder is measured to be 4236ppm, and the O content is 912ppm.

[0115] Step 3: Jet-mill the main and auxiliary powders. Grind the main alloy A hydrogenated powder to a D50 particle size of 3.89 μm using a jet mill, and the auxiliary alloy B hydrogenated powder to a D50 particle size of 2.73 μm using a jet mill. Mix the main phase powder A and auxiliary phase powder B in a weight ratio of 98:2. Add 0.06% of a liquid lubricant to each and stir for 3 hours.

[0116] Step 4: The mixed powder is oriented in a magnetic field with an oxygen content of less than 100 ppm and a magnetic field strength of 1.8 T. After pressing, it is vacuum-sealed and then isostatically pressed at a pressure of 180 MPa to a density of 4.4 g / cm 3 of the compact.

[0117] Step 5: Place the isostatically pressed compact in a vacuum sintering furnace for vacuum sintering and aging. The sintering process is 1072°C for 8 hours, and the sintering vacuum is better than 0.1 Pa. The aging process is 900°C for 3 hours, 650°C for 3 hours, and 495°C for 5 hours. Cooling during the second and third aging stages is performed using nitrogen-filled air cooling at a cooling rate of 12°C / min.

[0118] Example 7: Step 1: Prepare a low-heavy rare earth main alloy A and auxiliary alloy B, and respectively melt the prepared main alloy A and auxiliary alloy B raw materials into alloys by vacuum melting, and then cast them at high temperature to form main alloy A castings and auxiliary alloy B castings.

[0119] In order to obtain excellent microstructure, different process parameters are selected for the preparation of main alloy A and auxiliary alloy B. In this embodiment, the casting temperature of main alloy A is 1420℃~1450℃, the linear speed of the casting copper roller is 0.9~1.5m / s, and the cooling water temperature is 10℃~30℃. The thickness of the main alloy rapid solidification casting sheet obtained is 0.2mm~0.4mm, the grain spacing is 3.5~4.5μm, and it has an excellent columnar microstructure, as shown in the attached figure. Figure 1 As shown, the gray is (RE / RE')2Fe 14 Phase B, white, is a rare earth-rich phase.

[0120] The casting temperature of auxiliary alloy B is 1500℃~1520℃, the linear speed of the casting copper roller is 5~10m / s, and the cooling water temperature is 2℃~8℃ to obtain a fine and uniform microstructure with a thickness of 0.05mm~0.15mm and a grain spacing of 0.5~2μm.

[0121] In this embodiment, the weight percentages of the main alloy A are: 29% PrNd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, and 68.42% Fe. The weight percentages of the auxiliary alloy B are: 40% Dy, 47.5% Pr, 1% B, 4% Ti, 3% Cu, and 4.5% Ga. The specific compositions are shown in Table 1.

[0122] Step 2: Prepare hydrogen crushed powder, hydrogen crush the main alloy A casting, and the hydrogen absorption pressure is 1.8kg / cm 2 Until saturation, then dehydrogenation, the dehydrogenation temperature is 550 ℃, the obtained hydrogen powder has an O content of 852ppm and a H content of 780ppm; the hydrogen absorption pressure of the auxiliary alloy B casting is 3.5kg / cm 2 When absorbing hydrogen, it is first heated to 300℃ and kept warm for 0.5 hours before hydrogen is introduced. Then it is vacuumed and heated to 880℃ for secondary hydrogen absorption until saturation. Finally, it is kept warm at 450℃ for dehydrogenation. The dehydrogenation time is controlled reasonably. The final H content of the auxiliary phase hydrogen powder is measured to be 4236ppm, and the O content is 912ppm.

[0123] Step 3: Jet-mill the main and auxiliary powders. Grind the main alloy A hydrogenated powder to a D50 particle size of 3.89 μm using a jet mill, and the auxiliary alloy B hydrogenated powder to a D50 particle size of 2.73 μm using a jet mill. Mix the main phase powder A and auxiliary phase powder B in a weight ratio of 98:2. Add 0.06% of a liquid lubricant to each and stir for 3 hours.

[0124] Step 4: The mixed powder is oriented in a magnetic field with an oxygen content of less than 100 ppm and a magnetic field strength of 1.8 T. After pressing, it is vacuum-sealed and then isostatically pressed at a pressure of 180 MPa to a density of 4.4 g / cm 3 of the compact.

[0125] Step 5: Place the isostatically pressed compact in a vacuum sintering furnace for vacuum sintering and aging. The sintering process is 1072°C for 8 hours, and the sintering vacuum is better than 0.1 Pa. The aging process is 900°C for 3 hours, 650°C for 3 hours, and 495°C for 5 hours. Cooling during the second and third aging stages is performed using nitrogen-filled air cooling at a cooling rate of 12°C / min.

[0126] Comparative Example 1: A single alloy was prepared according to the theoretical composition of the main alloy A and the auxiliary alloy B in the mixing ratio of 98:2 in Example 1. The single alloy was then prepared into a fine powder according to the smelting, hydrogen crushing, and air flow milling process parameters of the main alloy A in Example 1. The single fine powder was then mixed, and the pressing and sintering processes were the same as those in Example 1. The specific composition is shown in Table 1.

[0127] Comparative Example 2: A single alloy was prepared according to the theoretical composition of the main alloy A and the auxiliary alloy B in the mixing ratio of 96:4 in Example 2. The single alloy was then finely powdered according to the smelting, hydrogen crushing, and jet milling process parameters of the main alloy A in Example 2. The single fine powder was then mixed, and the pressing and sintering processes were unchanged according to the processes in Example 2. The specific composition is shown in Table 1.

[0128] Comparative Example 3: A single alloy was prepared according to the theoretical composition of the main alloy A and the auxiliary alloy B in the mixing ratio of 98:2 in Example 3. Then, fine powder was prepared according to the smelting, hydrogen crushing, and air flow milling process parameters of the main alloy A in Example 3. Then, the single powder was mixed, and the pressing and sintering processes were the same as those in Example 3. The specific composition is shown in Table 1.

[0129] Comparative Example 4: A single alloy was prepared according to the theoretical composition of the main alloy A and the auxiliary alloy B in the mixing ratio of 96:4 in Example 4. Then, fine powder was prepared according to the smelting, hydrogen crushing, and air flow grinding process parameters of the main alloy A in Example 4. Then, the single powder was mixed, and the pressing and sintering processes were the same as those in Example 4. The specific composition is shown in Table 1.

[0130] The magnetic property test provided in the specific embodiment of the present invention is as follows: the main magnetic property test methods for varieties N, M, H, SH and UH materials are carried out in accordance with the provisions of GB / T 3217, and the main magnetic property test methods for EH and TH materials are carried out in accordance with the provisions of GB / T 29628; the magnetic property standard of neodymium iron boron is in accordance with GB / T 13560-2017.

[0131] The magnets of Examples 1-4 were tested for magnetic properties with the same composition as those of Comparative Examples 1-4. The comparative data are shown in Table 2.

[0132] Table 1 Mass percentage of each element in the embodiments and comparative examples:

[0133]

[0134] Table 2 Magnetic properties of examples and comparative examples

[0135]

[0136] Combining Tables 1 and 2, it can be seen that the magnetic properties of the magnet prepared by the preparation method of the present invention are Br, H cj The squareness value of the demagnetization curve is higher than that of the magnet produced by the existing method under the condition of the same ingredient composition. Under the premise of the same magnetic properties, the method of the present invention can reduce or even eliminate the use of heavy rare earth to achieve higher magnetic performance requirements.

[0137] At the same time, Figure 2 It can be seen that the microstructure of the NdFeB magnet of Example 1 includes the matrix ((RE / RE')2Fe 14 B) phase and rare earth-rich grain boundary phase. Figure 3 It can be seen from the microstructure of the magnet obtained by the existing dual alloy process technology that the grain boundary phase of the existing magnet is unevenly distributed around the matrix phase and has breakpoints. In the magnet prepared by the present invention, the grain boundary phase is more evenly distributed around the matrix phase.

[0138] The matrix phase accounts for 97.5% to 98% of the total volume fraction, the grain boundary phase accounts for 2% to 2.5% of the total volume fraction, and the matrix main phase ((RE / RE')2Fe 14 B) The grain size is about 8~12μm, and the width of the grain boundary phase is about 5~10nm.

[0139] The grain boundary phase is composed of a rare earth-rich phase. According to statistics, the mass ratio of Fe to RE / RE' in the rare earth-rich phase of Example 1 is w(Fe):w(RE / RE')=1:2. The chemical formula of the rare earth-rich phase is (RE / RE')Fe 1.3 , the specific chemical formula is PrFe 1.3 、NdFe1.3 、Dy Fe 1.3 、PrDyFe 1.3 、NdDyFe 1.3 、PrNdDy Fe 1.3 One or more of.

[0140] Example 2 The mass ratio of Fe to RE / RE' in the rare earth-rich phase is w(Fe):w(RE / RE')=1:2.5, and the chemical formula of the rare earth-rich phase is (RE / RE')Fe; the specific chemical formula may be one or more of PrFe, NdFe, DyFe, PrDyFe, NdDyFe, and PrNdDyFe.

[0141] In Example 3, the mass ratio of Fe to RE / RE' in the rare earth-rich phase is w(Fe):w(RE / RE')=1:6.0, and the chemical formula of the rare earth-rich phase is (RE / RE')2Fe; the specific chemical formula may be one or more of Pr2Fe, Nd2Fe, (PrNd)2Fe; in Example 4, the mass ratio of Fe to RE / RE' in the rare earth-rich phase is w(Fe):w(RE / RE')=1:7.5, and the chemical formula of the rare earth-rich phase is (RE / RE')3Fe; the specific chemical formula may be one or more of Pr3Fe, Nd3Fe, (PrNd)3Fe.

[0142] The present invention can be implemented in various ways and is not limited to the above-described embodiments and / or examples. A person skilled in the art will appreciate that the present invention can be implemented in other specific ways without changing the technical concept or essential features of the present invention. Therefore, it should be understood that the above-described embodiments and / or examples are illustrative and not intended to limit the present invention.

Claims

1. A high performance sintered NdFeB magnet, characterized in that: The raw materials for preparing the NdFeB magnet include a main alloy and an auxiliary alloy, wherein the auxiliary alloy does not contain Fe and Co elements; The main alloy comprises the following chemical components in terms of mass percentage: RE x B y M z T w F 1-x-y-z-w , RE is rare earth Nd or PrNd, B is boron, M is at least one of Nb, Zr, and Ti, T is Cu and Ga, and F contains Fe and Co, wherein the Co content is 0-3wt.%, and the Fe content is not 0, wherein the content of each element is x: 27-30wt.%, y: 0.9-1.1wt.%, z: 0.05-0.25wt.%, and w: 0.1-0.5wt.%; The auxiliary alloy comprises the following chemical components in terms of mass percentage: RE' 1-a-b-c B a M b c , RE' is one or more of Pr, Ho, Dy, Tb, B is boron, M is at least one of Nb, Zr, Ti, Cu and Ga, where the mass percentage of Cu and Ga is 1: (1.2~1.5), and the content of each element is a: 0.5~5wt.%; b: 0~2wt.%, c: 4~10wt.% The microstructure of the NdFeB magnet includes a matrix phase and a rare earth-rich grain boundary phase, wherein the matrix phase is (RE / RE')2(F) 14 B, wherein F is Fe and Co, the mass percentage content of Co is 0-3, the mass percentage of Fe and RE / RE' in the rare earth-rich grain boundary phase is 1: (1.4~8), wherein RE is Nd or PrNd, and RE' is one or more of Pr, Ho, Dy, and Tb.

2. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The NdFeB magnet is prepared by a double alloy process.

3. The high performance sintered NdFeB magnet according to claim 1, characterized in that: In the microstructure of the NdFeB magnet, the matrix phase accounts for 97.5% to 98%, and the mass percentage of the rare earth-rich grain boundary phase is 2% to 2.5%.

4. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The D50 particle size of the main alloy is 3.5-4.5 μm, and the D50 particle size of the auxiliary alloy is 2.5-3.5 μm.

5. The high performance sintered NdFeB magnet according to claim 1, characterized in that: In element T, the mass percentage of Cu and Ga is 1: (1.2~1.5).

6. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The mass ratio of the main alloy to the auxiliary alloy is (94-98): (2-6).

7. A method for preparing a high performance sintered NdFeB magnet according to any one of claims 1 to 6, characterized in that: include: S1. Prepare powders of the main alloy and auxiliary alloy according to any one of claims 1 to 6; S2. Evenly mixing the main alloy powder and the auxiliary alloy powder to obtain a mixed powder, and pressing the mixed powder into a compact by a magnetic field forming method or a hot pressing and hot deformation method; S4, sintering the compact into a blank in vacuum or inert gas; S5. Perform multi-stage aging treatment on the blank to obtain a high-performance sintered NdFeB magnet.

8. The method for preparing a high performance sintered NdFeB magnet according to claim 7, wherein: The multi-stage aging treatment includes three stages of aging treatment; Among them, the temperature of the first stage of aging treatment is 890~930℃; The temperature of the second aging treatment is 580~680℃; The temperature of the third aging treatment is 420~520℃.

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